Background: As the population ages, older adults are seeking meaningful, and impactful, post-retirement roles. As a society, improving the health of people throughout longer lives is a major public health goal. This paper presents the design and rationale for an effectiveness trial of Experience Corps™, an intervention created to address both these needs. This trial evaluates (1) whether senior volunteer roles within Experience Corps™ beneficially impact children's academic achievement and classroom behavior in public elementary schools and (2) impact on the health of volunteers. Methods: Dual evaluations of (1) an intention-to-treat trial randomizing eligible adults 60 and older to volunteer service in Experience Corps™, or to a control arm of usual volunteering opportunities, and (2) a comparison of eligible public elementary schools receiving Experience Corps™ to matched, eligible control schools in a 1:1 control:intervention school ratio. Outcomes: For older adults, the primary outcome is decreased disability in mobility and Instrumental Activities of Daily Living (IADL). Secondary outcomes are decreased frailty, falls, and memory loss; slowed loss of strength, balance, walking speed, cortical plasticity, and executive function; objective performance of IADLs; and increased social and psychological engagement. For children, primary outcomes are improved reading achievement and classroom behavior in Kindergarten through the 3rd grade; secondary outcomes are improvements in school climate, teacher morale and retention, and teacher perceptions of older adults. Summary: This trial incorporates principles and practices of community-based participatory research and evaluates the dual benefit of a single intervention, versus usual opportunities, for two generations: older adults and children.